The present invention relates to an optical element holding device, and more particularly, to a holding device that enables highly accurate adjustment of the position of an optical element. The present invention provides a holding device, a barrel including the holding device, an exposure apparatus including the barrel, and a device manufacturing method including exposure performed with the exposure apparatus.
In the prior art, a plurality of optical elements that form a projection optical system of a projection exposure apparatus are held by holding devices, which enable accurate adjustment of the positions of the optical elements in the optical axis direction and the attitudes of the optical elements, such as tilt. The adjustment of the positions and the attitudes of the optical elements corrects aberrations and controls aberration fluctuations, which would be caused by changes in atmospheric pressure and absorption irradiated heat.
A holding device for adjusting the position of an optical element through automatic control has been disclosed (refer to patent publication 1). The holding device includes an inner ring for holding the peripheral edge of a lens, and an outer ring arranged outside the inner ring connected to the inner ring. The outer ring includes an actuator. Displacement of the actuator is transmitted to the inner ring by a displacement enlargement mechanism so as to displace the lens. A sensor is attached to the outer ring to monitor the position of the lens. A barrel including the holding device is relatively compact.
To enable the manufacturing of high-density and fine-pitch semiconductor devices, projection exposure apparatuses are required to perform exposure with higher resolutions. There is a tendency for projection exposure apparatuses to use exposure light with shorter wavelengths. For example, the projection exposure apparatuses may use ArF excimer lasers (λ=193 nm) or F2 lasers (λ=157 nm). The use of exposure light with shorter wavelengths contributes to enhancing resolution.
When exposure light having a wavelength of 200 nm or shorter is used, the existence of absorption substances, such as water, oxygen, and organic substances, in the optical path of the exposure light, would greatly attenuate the intensity of the exposure light. In view of this, the holding device described in the patent publication 1 supplies purge gas into the barrel to remove water, oxygen, and organic substances, which that may be present in the optical path of the exposure light, from the barrel. However, a gap is formed between the outer ring and the actuator. The purge gas may leak from the gap or ambient air (gas including oxygen, water, and organic substances) may flow through the gap into the inner space of the barrel. Therefore, a jacket is arranged around the barrel, and the space surrounded by the jacket is filled with purge gas.
Patent Publication 1: U.S. Patent Publication No. 2001/0038500
The space surrounded by the jacket accommodates a signal communication coated cable, which is connected to the sensor, and a power feeding coated cable, which is connected to the actuator. The coated cables may generate a subtle amount of chemical pollutants (outgas), such as organic substances. The space surrounded by the jacket is connected to the inner space of the barrel through the gap described above. The subtle amount of chemical pollutants generated by the coated cables may flow from the space surrounded by the jacket into the inner space of the barrel through the gap described above, and may absorb the exposure light or cause loss of transparency of the lenses accommodated in the barrel.